1. The Field of the Invention
This invention relates to the field of object-oriented databases wherein navigation between objects is a fundamental method for finding desired data. More specifically, this invention relates to the methods and structures for creating relationships between software objects in order to assist in object navigation.
2. Present State of the Art
Object-oriented systems, including databases, have become prevalent in recent years as a significant design technique that allows high degrees of code reusability between projects and for modeling real world solutions to problems in a more natural way. A software object is composed of data and methods to operate on or manipulate the data and otherwise give the object its "behavior."
In many database applications, it is useful to create a relationship between objects that a client may navigate from one object to another based on the relationship. The usefulness of relationship navigation derives in part from the different types of objects and their arrangement with respect to one another in forming "models" as part of an implemented software solution. For example, software objects used to present the various pieces in a development environment database would tend to have some very natural relationship. In such a database, an object representing a C++ source file would be related to other objects representing header files and to compiled code generated from the source file.
Relationships allow focused navigation through an object database. For example, a client testing the current state of a completed application in the development environment database would traverse or navigate the relationships between the objects representing the constituent parts to determine which modules would require recompilation or other action.
Furthermore, searches may be made on specific types of relationships to identify objects having a particular characteristic in the structured hierarchy of related objects. The relationship itself becomes an attribute that distinguishes the object.
In some database applications, it is only the state of an object that is stored in a repository. A software client will access the object state by instantiating an object having the assigned state and manipulate the object in order to operate on that state. Other objects may be instantiated as necessary through object methods to gain access to other object states and for navigating through the database. The key to navigating the database are methods that will instantiate necessary objects to traverse relationships between related objects.
By allowing relationships between objects, structure is added to a database of objects and hence greater meaning can be given to the objects and the information represented therein. This allows object-oriented databases to more closely mimic structure and relationships found in the real world problems that object-oriented software products are intended to model.
Currently, relationships or links between objects are made on the entire object, usually defined in the class used to create the object upon instantiation. While this allows relationships to exist between objects, it lacks granularity for allowing objects of different types to be conventionally related without minimizing object functionality or increasing object overhead.
Ways are often sought to present an intuitive model for incrementally adding functionality into objects. One successful approach has been an object system where each object is composed of multiple interfaces, each interface representing a quantum of related functionality. An object is built of necessary interfaces for giving the object the desired character or behavior. It would be advantageous to incorporate relationship behavior on such interfaces to thereby allow interfaces to define relationships rather than object classes.
Methods of creating, managing and defining object relationships are sought that increase system efficiency, expand potential functionality, are easily extensible, and otherwise add capabilities to object oriented designs. Those methods that allow greater flexibility and the ability to easily relate objects of different types (i.e., those created or instantiated by different classes) to be easily related based on object characteristics rather than the mechanical creation mechanisms are particularly important.